1. Field of Invention
The present invention relates generally to data communication systems. More particularly, the present invention relates to systems and methods for allowing the frame format of a signal received on a port to be determined in real-time and to perform actions based upon the determined frame format.
2. Description of the Related Art
The demand for data communication services is growing at an explosive rate. Much of the increased demand is due to the fact that more residential and business computer users are becoming connected to the Internet. Furthermore, the types of traffic being carried by the Internet are shifting from lower bandwidth applications towards high bandwidth applications which include voice traffic and video traffic.
DS3 traffic is a prevalent type of traffic in large networks. A DS3 signal generally has a bandwidth of approximately 44.736 megabits per second (Mbps), and may carry twenty eight DS1 signals. DS3 line cards which support DS3 traffic allow routers within a network to be connected to high-speed DS3 leased line services. In general, DS3 line cards include ports that are used to receive DS3 signals.
A DS3 signal generally includes multiple frames which contain series of bits that are arranged as rows of data. A frame in a DS3 signal includes 4760 bits that are divided into seven rows, or subframes, of data. The bits included in a frame include overhead bits and payload bits. The overhead bits include frame boundary bits which enable payload bits to be extracted from the frame correctly. Each frame includes twenty-one C-bits, which may be used as stuff control bits for an M23 framing format to indicate how bits are stuffed in a frame, as will be appreciated by those skilled in the art. In other words, C-bits may identify the contents of M23 stuff bits. C-bits may also be used to account for rate differences in the transmission of frames in an M23 format.
DS3 signals typically have three possible frame or framing formats, namely a C-Bit parity or C-Bit format, an M23 format, or an unframed format. A signal with a C-bit frame format generally uses C-bits for purposes other than identifying the contents of stuff bits, since there are no stuff bits in a C-Bit format. For example, C-bits in frames of a signal that is of a C-Bit format may provide path parity information, and status information to initiate remote loops. A signal of an M23 format generally includes a multiplexed scheme which provides for transmission of seven DS2 channels.
Properly identifying a frame format for a DS3 signal or DS3 traffic is generally necessary in order to enable a port on which the DS3 signal is to be received to be properly configured. When a port is configured or provisioned incorrectly, the payload of received frames may be corrupted as some bits may be interpreted as being payload bits when those bits are not part of the payload. By way of example, as part of C-bit usage, a frame that is of a C-Bit format generally includes a far end loopback mechanism, while a frame that is of an M23 format does not use a loopback mechanism as a part of C-bit usage. Hence, provisioning a port to expect a signal of a C-Bit format when a signal of an M23 format is received may result in the signal being misread.
FIG. 1a is a process flow diagram which illustrates the steps associated with one conventional method of provisioning a DS3 port. A provisioning process 102 begins at step 104 in which a network administrator determines a signal type, or the format of a signal, that is to be received on a DS3 port. As will be appreciated by those skilled in the art, a trial and error process is often used to provision a DS3 port to be consistent with a particular format. That is, a network administrator may essentially guess what the format of an expected signal will be, then provision the DS3 port accordingly. Alternatively, a network administrator may contact the network administrator associated with a system which is to transmit a signal to the port, and ask that network administrator about the frame format of the signal that is to be transmitted. Contacting a network administrator is often be inconvenient and inefficient, particularly when there are multiple ports to be configured.
Once the network administrator determines the format of the signal, then the network administrator manually configures the port in step 108. Methods used to configure a port are well-known to those skilled in the art. After the port is configured, the process of provisioning a port is completed.
FIG. 1b is a process flow diagram which illustrates the steps associated with a second conventional method of provisioning a DS3 port. A provisioning process 120 begins at step 122 in which a network administrator installs a test set on a DS3 line which is in communication with a port that is configured to receive a signal. In other words, the test set is installed within a DS3 circuit path. After the test set is installed, a signal is received on the DS3 line and, hence, by the test set, in step 126. The test set then determines that type of signal that is being received on the port in step 130. As will be appreciated by those of skill in the art, some test sets may not be arranged to determine signal types.
Once the test set determines the frame format of the signal that is being received on the port in step 130, the port is configured in step 134. In general, the port may be manually configured by the network administrator. The port is typically configured to be consistent with the frame format determined by the test set. After the port is configured, the network administrator generally uninstalls the test set in step 138, and the process of provisioning a port is completed. It should be noted that once the port is provisioned, originating DS3 equipment is connected or reconnected to the port.
While a test set is generally effective in determining the format of a DS3 signal that is to be received on a port, test sets or test equipment is often relatively expensive. As DS3 lines and DS3 traffic are prevalent in networks, many systems would generally require multiple test sets to detect the frame format associated with DS3 lines, as well as to provision ports associated with DS3 lines. In particular, when multiple lines carry DS3 traffic, multiple test sets are typically needed if the frame format of every line is to be determined, unless one or a few tests sets are sequentially used on each of the multiple lines. Hence, the proliferation of test sets often proves to be expensive and, in a case in which a single test set is used sequentially, time-consuming.
Further, tests sets generally must be positioned on a DS3 line or within a DS3 circuit path in order for the test set to accurately monitor the frame format of signals within the path. Positioning tests set within a DS3 circuit path, as for example to obtain frame format information while signals are substantially continuously being sent through the circuit path, is a relatively intrusive process. In addition to being intrusive, positioning test sets within a DS3 circuit path is often also a time-consuming and, hence, an inefficient, process.
Therefore, what is needed is an efficient, inexpensive method for detecting the frame format of a DS3 signal. Specifically, what is desired is a convenient, relatively inexpensive method for automatically detecting the frame format of a DS3 signal, and for automatically provisioning a port which receives the DS3 signal.